Base for a spherical container

ABSTRACT

When mounting a big spherical container on a base or foundation the bottom of the container has often to be provided with reinforcements. Such reinforcements can be omitted if the upper surface of the base has the general shape of a sphere, the radius of said sphere exceeding the radius of the container to such an extent that the weight of the container is substantially evenly distributed on the base when the container is filled to its maximal weight.

United States Patent Eriksson et a1.

BASE FOR A SPHERICAL CONTAINER Per-0101 Eriksson, Sandviken; Finn Borslun, Degerfors, both of Sweden Uddeholme Aktiebolag, Uddeholm, Sweden Filed: Aug. 21, 1967 Appl. No.: 662,176

lnventors:

[73] Assignee:

Foreign Application Priority Data Aug. 25, 1966 Sweden ..l1505/66 References Cited UNITED STATES PATENTS 929,542 7/1909 Boermel ..220/ 69 1,670,024 5/1928 Day 1,732,829 10/ 1929 Boardman ..248/ 146 Feb. 22, 1972 1,958,421 5/ 1934 Daniels "220/1 B 2,302,802 1 H1942 Roberts .248/ 350 2,313,823 3/ 1943 Harrigan ..248/ 350 2,363,992 1 1/1944 Reiser ..248/ 146 2,870,982 1/1959 Greene et a1. .....248/l46 2,988,333 6/1961 Mesic ..248/146 3,043,465 7/ 1962 Homer ..220/69 FOREIGN PATENTS OR APPLICATIONS 959,166 5/ 1964 Great Britain ..248/ 146 Primary Examiner-Francis K. Zugel Attorney-Pierce, Scheffler and Parker [57] ABSTRACT When mounting a big spherical container on a base or foundation the bottom of the container has often to be provided with reinforcements. Such reinforcements can be omitted if the 4 Claims, 3 Drawing Figures BASE FOR A SPHERICAL CONTAINER The invention is concerned with a base or foundation for a spherical container. It is known that a spherical container can be mounted on legs or on a cylindrical collar. However, the zone where the wall of the container is in contact with the legs or the collar is subjected to a heavy load, and therefore the container has usually to be reinforced in said zone. It is possible to distribute the load on the wall of the container in a more even way if the container is mounted on a base having an upper spherical surface conforming to the surface of the container. Nevertheless, there is in very big containers the danger that the wall will be subjected to unallowed stress and deformation (buckling), particularly the wall portion adjacent the edge of the base.

The invention is based upon the fact that a spherical container made of steel, has a certain degree of elasticity. Therefore, the shape of the container when empty is different from the shape of the container when filled. It is the general object of the invention to provide a base which permits said elastic deformation of the container to take place. The base shall be able to carry the container, empty as well as filled, without creating any permanent deformation of the wall of the container. It cannot be avoided that the pressure between the container and the base creates stresses in the wall of the container, but said stresses shall not be allowed to exceed the yield point ofthe material.

It is a particular object of the invention to provide a base which does not require any reinforcement of the container.

The maximal internal pressure of a container, for instance the hydrostatic pressure, necessitates a certain predetermined wall thickness. The pressure between the container and the base of this invention does not require any increase of said predetermined wall thickness, or any other reinforcement.

The invention is concerned with giving the upper surface of the base a shape eliminating the danger of fracture or deformation of the wall of the container, even in very big containers. It has been found, according to the present invention, that the upper surface of the base shall have the general shape of a sphere. and that the radius of said sphere shall be slightly longer than the radius of the container. A base, thus shaped, supports the spherical container with the weight of the container being substantially evenly distributed on the contact area between the container and the base. According to a preferred embodiment of the invention the upper surface of the base, as defined by means of a vertical section through the center of the base, shall have the general shape of a circle having the same radius as the container when unloaded, but the exact shape of said upper surface of the base shall deviate from the shape of said circle, the curve defining said deviation being within the hatched area of FIG. 1 of the accompanying drawing in which the abscissa represents the radius of the base, in millimeters, and the ordinate represents said deviation, one unit on the ordinate representing millimeters the base, in millimeters. R, is the external radius of the base, in

millimeters, and R, is the radius of the central recess, if any, of the base in millimeters.

If the base has a central recess it is preferred to choose a deviation approximately as represented by the curve 8 in FIG. 1. The deviation at the inner edge of the base, that is at the radius R,, is comparatively large. The deviation has a minimum approximately halfway between R, and R,,. At the outer edge of the base, that is at the radius R,,, the deviation has a value higher than that of the inner edge.

In a base having no recess, that is R,=0, it is preferred to choose a deviation approximately as represented by the curve 9 in FIG. 1. The deviation is substantially constant from the center of the base, where R O, up to approximately 0.7 R,,, and increases to a highest value at the radius R,,, that is at the edge of the base.

The invention makes it possible to support a spherical container on a circular base having a radius much below that of the container. Preferably, the external radius of the base should not be more than 0.6 times the radius of the container. If the base contains a central recess said recess should preferably have a radius less than 0,75 times the external radius of the base. Further, the radius of the recess and the external radius of the base should preferably be chosen to satisfy the equation: I

R -R Sp (R/IV- 1.25 I0" F (2) in which Sp is the desired safety factor against the deformation of a filled container.

The entire upper surface of the base is in contact with the container only when the container has its maximal weight, the weight of the container being evenly distributed on the surface of the base. When the container is empty or filled only to a part of its full capacity, it is in contact with a portion of the base only.

When mounting a container on a base of the invention it is desired to apply a layer of a comparatively soft material betweenthe container and the base, such as rubber, cardboard, plastics or the like. Said layer compensates for local defects in the shape of the container and the base. The layer also adds a heat insulation between the container and the base. The layer also permits a movement between the container and the base, for instance a movement produced by variations in temperature. It has been found that a useful layer consists of oil-resistant rubber having a surface layer of graphite and a corrosion-inhibiting fat.

The invention will now be explained with reference to an example. Reference is also being made to the accompanying drawing. FIG. 1 illustrates the diagram showing the deviation of the surface of the base from the spherical shape FIG. 2 illustrates a corresponding diagram, numerical values having been added to illustrate the example which will be described below. FIG. 3 illustrates a vertical cross section through a base of this invention and a portion ofa container supported by said base.

It is desired to build a spherical container to contain 3,000 metric tons of a liquid having a density of approximately 0.6 kgJdm. (kilogram/cubic decimeter). The external radius of the container shall be 10,800 millimeters. The material of the container is a pressure vessel steel having a modulus of elasticity of 2 l ,000 kp./mm. The maximal pressure inside the container requires a wall thickness of 31 millimeters. An insulating layer is to be applied between the container and the base. Said insulating layer is to have a thickness of 20 millimeters, and is to be coated with graphite and a corrosion-inhibiting fat. It is desired that the container shall be subjected to a hydrostatic test pressure when filled with water. The container has its maximal weight when filled with water, viz. 5.55 10 kilograms. When the container is subjected to said hydrostatic test pressure it is desired that the safety factor against deformation (buckling) shall be 2.4. The container when filled with the normal liquid weighs 3.3 10 kilograms, resulting in a safety factor against deformation of 4.

It is desired that the base shall have a central recess having a radius of 2,000 millimeters. Formula No (2) is now used for calculating the external radius of the base, resulting in a value of 4,920 millimeters. A somewhat higher value is chosen, viz. 5,000 millimeters. The term No. (I) can now be calculated, resulting in avalue of 15.7 millimeters. It is now possible to calculate the numerical values for the corners of the hatched area of FIG. 1. The abscissa of corner 7 is 5,000, since R 5,000. The ordinate of corner 7 is 15.7, since the ordinate 1.0 according to FIG. 1 has to be multiplied by. 15.7, that is the value of term (1). The abscissa and ordinate values of all the other corners of the hatched area have been calculated in the same way, and the numerical values have been added to the diagram of FIG. 2.

In this particular example it is preferred to choose the shape represented by the curve 8 inside the hatched area. A templet is now made in accordance to said curve, and the templet is then used in shaping the upper surface of the base, which preferably consists of concrete.

The base of the invention is illustrated in FlGv 3. The base 1 has a central recess 5. This central recess is preferably used for housing the pumps and other auxiliary equipment used in the operation of the container. The upper surface 2 of the base has been calculated and made as described above. An insulating layer 4, covered with a corrosion-inhibiting fat and graphite, has been applied on the surface 2. A container 3 is mounted on the base 1. The container, when empty, has a perfectly spherical bottom 3h. The bottom of the empty container is in contact with only a limited portion 4a of the insulating layer 4. When the container is being filled with a liquid the contact area 40 increases, When the container has been filled to its maximal capacity, the increased weight has resulted in an elastic deformation of the container, the new shape of the bottom of the container being designated 3a. ln this filled condition the bottom 3a is in contact with the entire surface of the insulating layer 4, and the weight of the container is substantially equally distributed on the surface of the base. A collar 6 has been welded to the bot om of the container. The collar protrudes into the recess 5, and thus prevents the container from rotating on the base.

If the container described in the above Example had been mounted upon legs in the conventional way, it would have been necessary to provide a large number of legs, for instance 16 legs, requiring a much more complicated and expensive structure than the base of this invention.

What is claimed is:

l. A base for a spherical container, particularly, a very big container, said base having a circular horizontal cross section and being, if desired, provided with a central recess, the base having an upper surface deviating from the shape of the unloaded container, the radius of curvature in every point of the surface of the base being larger than the external radius of the container, the curve defining the deviation from the unloaded spherical container being arcuate and within the hatched area of FIG. 1 of the accompanying drawing in which the abscissa represent the radius of the base in millimeters, and the ordinates represent said deviation, one unit of the ordinate representing in which P represents the maximal weight, in kilograms, of the container including its contents; R is the external radius of the container, in millimeters; E is the modulus of elasticity of the material of the container, in kp./mm. is the thickness of the wall of the container adjacent the base, in millimeters; R, is the external radius of the base, in millimeters; and R, is the radius of the central recess, if any, of the base, the curve within said hatched area counted from R, to R first continuously falling to a minimum on the abscissa and then again continuously raising whereby when the container is filled to its maximal weight the container is substantially evenly distributed on said base.

2. A base as defined in claim 1, characterized in that R, 0.6 R.

3. A base as claimed in claim 1 and having a central recess, characterized in that R, 0.75 R,

4. A base as claimed in claim 1, characterized in that 

1. A base for a spherical container, particularly, a very big container, said base having a circular horizontal cross section and being, if desired, provided with a central recess, the base having an upper surface deviating from the shape of the unloaded container, the radius of curvature in every point of the surface of the base being larger than the external radius of the container, the curve defining the deviation from the unloaded spherical container being arcuate and within the hatched area of FIG. 1 of the accompanying drawing in which the abscissa represent the radius of the base in millimeters, and the ordinates represent said deviation, one unit of the ordinate representing in which P represents the maximal weight, in kilograms, of the container including its contents; R is the external radius of the container, in millimeters; E is the modulus of elasticity of the material of the container, in kp./mm.2; t is the thickness of the wall of the container adjacent the base, in millimeters; Ry is the external radius of the base, in millimeters; and Ri is the radius of the central recess, if any, of the base, the curve within said hatched area counted from Ri to Ry first continuously falling to a minimum on the abscissa and then again continuously raising whereby when the container is filled to its maximal weight the container is substantially evenly distributed on said base.
 2. A base as defined in claim 1, characterized in that Ry < or = 0.6 R.
 3. A base as claimed in claim 1 and having a central recess, characterized in that Ri < or = 0.75 Ry
 4. A base as claimed in claim 1, characterized in that in which SF is the desired safety factor against deformation of a filled container. 